Optical Disk Drive and Method for Performing Layer Jumps

ABSTRACT

The invention provides a method for performing a layer jump of a disk. First, a tracking error generation method is determined according to a layer type of a target layer when the layer jump is performed. A tracking error signal is then generated according to the tracking error generation method.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/290,979, filed on Dec. 30, 2009, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to optical disk drives, and more particularly to tracking operations of optical disk drives.

2. Description of the Related Art

A multi-layer disk comprises a plurality of layers for storing data. Multi-layer disks can be divided into two categories. In one category, the type of the layers of a multi-layer disk for storing data is the same. For example, a BD-ROM dual-layer disk has two BD-ROM layers, a BD-RE dual-layer disk has two BD-RE layers, and a BD-R dual-layer disk has two BD-R layers. In another category, the type of the layers of a multi-layer disk for storing data is different. For example, a BD Inter-Hybrid disk comprises a BD-ROM layer and at least one DVD-ROM layer. A BD Intra-Hybrid disk comprises a BD-ROM layer and a BD-RE layer.

When a multi-layer disk is inserted into an optical disk drive, the optical disk drive must access data from all layers of the multi-layer disk. When the optical disk drive projects a laserbeam on a first layer of the multi-layer disk, the optical disk drive can access data from the first layer according to reflection from the first layer. If data of a second layer of the multi-layer disk is to be subsequently access, the optical disk drive must then perform a layer jump operation to move a focus spot of the laserbeam from the first layer to the second layer. An optical disk drive therefore often performs layer jump operations when a multi-layer disk is accessed.

A tracking error signal is generated to enable a laserbeam move along a track of a layer of a disk. The tracking error signal can be generated according to differential phase detection (DPD) method or a differential push-pull (DPP) method. When a layer jump operation is performed to move a focus spot of a laserbeam from a first layer to a second layer of a multi-layer disk, if the first layer and the second layer are of the same type, the method initially used for generating a tracking error signal corresponding to the first layer is not changed and is directly used to generate a tracking error signal corresponding to the second layer. If the first layer and the second layer are of different types, the method initially used for generating a tracking error signal corresponding to the first layer may be not suitable for generating a tracking error signal corresponding to the second layer.

For example, a BD Intra-Hybrid disk comprises a BD-ROM layer and a BD-RE/R layer. A differential push-pull (DPP) method should be used for generating a tracking error signal corresponding to the BD-RE/R layer, and a differential phase detection (DPD) method should be used for generating a tracking error signal corresponding to the BD-ROM layer. When an optical disk drive performs a layer jump to move a laserbeam from the BD-RE/R layer to the BD-ROM layer, if the initial DPP method corresponding to the BD-RE/R layer is used (without adjustment) to generate a tracking error signal corresponding to the BD-ROM layer, the tracking error signal would have a small amplitude, and comprise a lot of noise, and would not be able to be used for correctly moving the laserbeam along a track of the BD-ROM layer.

Similarly, when the optical disk drive performs a layer jump to move the laserbeam from the BD-ROM layer to the BD-RE/R layer, if the initial DPD method corresponding to BD-ROM layer is used (without adjustment) to generate a tracking error signal corresponding to the BD-RE/R layer, the tracking error signal would have a small amplitude, and comprise a lot of noise, and would not be able to be used for correctly moving the laserbeam along a track of the BD-RE/R layer. Thus, a method for generating a correct tracking error signal when a layer jump is performed is required.

BRIEF SUMMARY OF THE INVENTION

The invention provides a method for performing a layer jump of a disk. First, a tracking error generation method is determined according to a layer type of a target layer when the layer jump is performed. A tracking error signal is then generated according to the tracking error generation method.

The invention also provides an optical disk drive for performing a layer jump. In one embodiment, the optical disk drive comprises a first tracking error generator, a second tracking error generator, a decision module, and a multiplexer. The first tracking error generator generates a first tracking error signal according to a differential phase detection (DPD) method. The second tracking error generator generates a second tracking error signal according to a differential push-pull (DPP) method. The decision module determines a tracking error generation method according to a layer type of a target layer of a disk when the layer jump is performed. The multiplexer then selects a tracking error signal from the first tracking error signal and the second tracking error signal according to the tracking error generation method.

The invention provides a method for performing a layer jump of a disk. In one embodiment, the disk comprises only a BDROM layer and a BD-RE/R layer. A tracking error generation method is switched between a differential phase detection (DPD) method and a differential push-pull (DPP) method when the layer jump is performed. A tracking error signal is then generated according to the tracking error generation method.

The invention provides an optical disk drive for performing a layer jump on a disk. In one embodiment, the disk comprises only a BDROM layer and a BD-RE/R layer, and the optical disk drive comprises a first tracking error generator, a second tracking error generator, a switch module, and a multiplexer. The first tracking error generator generates a first tracking error signal according to a differential phase detection (DPD) method. The second tracking error generator generates a second tracking error signal according to a differential push-pull (DPP) method. The switch module switches a tracking error generation method between the DPD method and the DPP method when the layer jump is performed. The multiplexer then selects a tracking error signal from the first tracking error signal and the second tracking error signal according to the tracking error generation method.

A detailed description is given in the following embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1A is a schematic diagram for generating a tracking error signal according a differential push-pull (DPP) method;

FIG. 1B is a schematic diagram for generating a tracking error signal according a differential phase detection (DPD) method;

FIG. 2 is a flowchart of a method for performing a layer jump operation according to the invention;

FIG. 3 is a flowchart of another embodiment of a method for performing a layer jump operation according to the invention;

FIG. 4 is a block diagram of an optical disk drive performing a layer jump operation according to the invention;

FIG. 5 is a block diagram of another embodiment of an optical disk drive performing a layer jump operation according to the invention;

FIG. 6 is a flowchart of another embodiment of a method for performing a layer jump operation according to the invention;

FIG. 7 is a flowchart of another embodiment of a method for performing a layer jump operation according to the invention;

FIG. 8 is a block diagram of another embodiment of an optical disk drive performing a layer jump operation according to the invention; and

FIG. 9 is a block diagram of another embodiment of an optical disk drive performing a layer jump operation according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

Referring to FIG. 1A, a schematic diagram for generating a tracking error signal according a differential push-pull (DPP) method is shown. An optical disk drive projects a main-beam 100 and two sub-beams 102 and 104 on a track of a BD-RE layer of a blu-ray disk. A groove on the BD-RE layer forms the track. The main-beam 100 is projected on the groove of the track, and the two side-beams 102 and 104 are projected on the two sides of the groove. Four photodetectors respectively detect signal strength of a portion of the reflection of the main-beam 100 to obtain signals A, B, C, and D. Two photodetectors detect signal strength of the reflection of the sub-beam 102 to obtain signals E and F, and two photodetectors detect signal strength of the reflection of the sub-beam 104 to obtain signals G and H. The sum of the signals C and D are then subtracted from the sum of the signals A and B to obtain a signal [(A+B)−(C+D)]. The sum of the signals E and G are then subtracted from the sum of the signals F and H to obtain a signal [(F+H)−(E+G)]. The signals [(A+B)−(C+D)] and [(F+H)−(E+G)] are then added to obtain a tracking error signal of a differential push-pull method.

Referring to FIG. 1B, a schematic diagram for generating a tracking error signal according to a differential phase detection (DPD) method is shown. An optical disk drive projects a main-beam 100 on a track of a BD-ROM layer of a blu-ray disk. Data is recorded on a track on the BD-ROM layer in a form of a series of pits and lands which correspond to bits 0 and 1. The main-beam 110 is projected on the track, and four photodetectors respectively detect signal strength of a portion of the reflection of the main-beam 110 to obtain signals A, B, C, and D. When the main-beam 110 moves along the track (i.e. tracking on), the phases of the signals A, B, C, and D differ from each other, and the optical disk drive derives a tracking error signal from the phase difference between the signals A, B, C, and D according to a differential phase detection method.

Referring to FIG. 2, a flowchart of a method 200 for performing a layer jump operation according to the invention is shown. Assume that a disk comprises a plurality of layers. A laserbeam of an optical disk drive is currently projected on an initial layer of the disk, and the optical disk drive wants to perform a layer jump operation to project the laserbeam to a target layer of the disk. When the layer jump operation starts, the optical disk drive first focuses the laserbeam on the target layer of the disk (step 202). The optical disk drive then determines a tracking error generation method according to a type of the target layer (step 204). In one embodiment, when the target layer is a BD-ROM layer, the optical disk drive determines the tracking error generation method to be a differential phase detection (DPD) method. When the target layer is a BD-RE layer or a BD-R layer, the optical disk drive determines the tracking error generation method to be a differential push-pull (DPP) method.

The optical disk drive then generates a tracking error signal according to the tracking error generation method (step 206). Because the tracking error generation method has been appropriately determined according to the layer type of the target layer at step 204, the tracking error signal generated according to the tracking error generation method conforms to the properties of the target layer, has large amplitude, and comprises low noise. The optical disk drive can therefore successfully move the laserbeam along a track of the target layer according to the tracking error signal (step 208). In one embodiment, the optical disk drive derives a tracking control output (TRO) signal from the tracking error signal and uses the tracking control output signal to control the actuators of a pickup head for emitting the laserbeam along the track of the target layer. When the laserbeam is smoothly moved along the track of the target layer, the optical disk drive can receive the reflection of the laserbeam from the target layer and decode the reflection to obtain data stored on the track. Thus, completing the layer jump operation.

Referring to FIG. 3, a flowchart of another embodiment of a method 300 for performing a layer jump operation according to the invention is shown. The method 300 comprises the same steps as the method 200 shown in FIG. 2. According to the method 200 shown in FIG. 2, when a layer jump operation is performed, a laserbeam is first focused on a target layer of a disk (step 202), and a tracking error generation method is then determined according to a format of the target layer (step 204). On the contrary, according to the method 300 shown in FIG. 3, when a layer jump operation is performed, a tracking error generation method is first determined according to a type of a target layer (step 302), and the laserbeam is then focused on the target layer (step 304). In other words, the order of steps 202 and 204 is switched in a layer jump process according to the method 300.

Therefore, the tracking error generation method is determined during a period when the laserbeam is focused from the initial layer (i.e. current layer) to the target layer, or during a period when the laserbeam is re-focused on the target layer.

Referring to FIG. 4, a block diagram of an optical disk drive 400 performing a layer jump operation according to the invention is shown. In one embodiment, the disk is a BD Intra Hybrid disk. The optical disk drive 400 performs a layer jump operation according to the methods 200 or 300. In one embodiment, the optical disk drive 400 comprises a pickup head 402, a radio frequency (RF) amplifier 404, a tracking error compensator 406, a actuator driver 408, a DPD tracking error generator 412, a DPP tracking error generator 414, a multiplexer 416, and a decision module 418. When a layer jump operation is performed, the pickup head 402 focuses a laserbeam on a target layer of a disk 450, and detects reflection from the target layer to obtain a signal S₁. The RF amplifier 404 then amplifies the signal S₁ to obtain a signal S₂. The DPD tracking error generator 412 then uses a differential phase detection method to synthesize a first tracking error signal TE_(DPD) according to the signal S₂. The DPP tracking error generator 414 then uses a differential push-pull method to synthesize a second tracking error signal TE_(DPP) according to the signal S₂.

The decision module 418 then selects a tracking error generation method from the DPD method and the DPP method according to a layer type of the target layer, and then generates a signal K to indicate the tracking error generation method. In one embodiment, the decision module 418 determines the tracking error generation method to be the differential phase detection method when the target layer is a BD-ROM layer, and determines the tracking error generation method to be a differential push-pull method when the target layer is a BD-RE layer or a BD-R layer. The multiplexer 416 then selects a tracking error signal TE from the first tracking error signal TE_(DPD) and the second tracking error signal TE_(DPP) according to the signal K generated by the decision module 418. A plurality of compensator parameters of the TE compensator 406 is also determined according to the tracking error generation method. The TE compensator 406 then generates a tracking control output signal TRO according to the tracking error signal TE and the compensator parameters for moving the laserbeam along a track of the target layer. In one embodiment, the tracking control output signal TRO is sent to the actuator driver 408, and the actuator driver 408 then controls the actuators of pickup head 402 along the track of the target layer according to the tracking control output signal TRO.

Referring to FIG. 5, a block diagram of another embodiment of an optical disk drive 500 performing a layer jump operation according to the invention is shown. The optical disk drive 500 also performs a layer jump operation according to the methods 200 or 300. The optical disk drive 500 comprises all component modules of the optical disk drive 400 shown in FIG. 4. The decision module 518 has more functions than the decision module 418. When a layer jump operation is performed, the decision module 518 determines a tracking error generation method and generates a signal K according to a type of a target layer. Because a tracking error signal generated according to a DPP method is a sine wave and a tracking error signal generated according to a DPD method is a triangle wave, the TE compensator 506 must process the selected tracking error signal TE according to the tracking error generation method. The decision module 518 further determines a plurality of compensator parameters for the TE compensator 506 according to the tracking error generation method. The tracking error compensator 506 then adjusts a gain and a phase of the tracking error signal TE according to the compensator parameters, and then generates a tracking control output signal TRO according to the adjusted tracking error signal.

In addition, but not necessary, the optical disk drive 500 further comprises a focusing error generator module 522 and a focusing error compensator 524. The focusing error generation module 522 generates a focusing error signal FE according to the signal S₂. The focusing error compensator 524 then generates a focus control output signal FRO according to the focusing error signal FE, and the focus control output signal FRO is sent to an actuator driver 508 for focusing a laserbeam on the target layer before or after the decision module 518 determines the tracking error generation method.

Referring to FIG. 6, a flowchart of another embodiment of a method 600 for performing a layer jump operation according to the invention is shown. Assume that a disk inserted in an optical disk drive is a BD Intra-Hybrid disk which comprises only a BD-ROM layer and a BD-RE/R layer. Also, a laser beam of the optical disk drive is projected on a layer of the disk, and a layer jump operation to project the laserbeam to the other layer, referred to as a target layer, of the disk is to be performed by the optical disk drive. When the layer jump operation starts, the optical disk drive first focuses the laserbeam on the target layer of the disk (step 602). The optical disk drive then switches a tracking error generation method between a differential phase detection (DPD) method and a differential push-pull (DPP) method (step 604). Because the disk only comprises a BD-ROM layer and a BD-RE/R layer, when the layer jump operation is performed from the BD-ROM layer to the BD-RE/R layer, the tracking error generation method is automatically switched from a DPD method to a DPP method. When the layer jump operation is performed from the BD-RE/R layer to the BD-ROM layer, the tracking error generation method is automatically switched from a DPP method to a DPD method. The optical disk drive then generates a tracking error signal according to the tracking error generation method (step 606). Because the tracking error generation method has been appropriately changed at step 604, the tracking error signal generated according to the tracking error generation method conforms to the properties of the target layer, has a large amplitude, and comprises low noise. The optical disk drive can therefore successfully move the laserbeam along a track of the target layer according to the tracking error signal (step 608). Thus, completing the layer jump operation.

FIG. 7 is a flowchart of another embodiment of a method 700 for performing a layer jump operation according to the invention. In the method 700, the order of the steps 602 and 604 are exchanged to be steps 702 and 704 respectively, and steps 706 and 708 are same as steps 606 and 608 respectively.

Referring to FIG. 8, a block diagram of another embodiment of an optical disk drive 800 performing a layer jump operation according to the invention is shown. A disk 850 is a BD Intra Hybrid disk and comprises only a BD-ROM layer and a BD-RE/R layer. The optical disk drive 800 performs a layer jump operation according to the methods 600 or 700. In one embodiment, the optical disk drive 800 comprises a pickup head 802, a radio frequency (RF) amplifier 804, a tracking error compensator 806, an actuator driver 808, a DPD tracking error generator 812, a DPP tracking error generator 814, a multiplexer 816, and a switch module 818. When a layer jump operation is performed, the pickup head 802 focuses a laserbeam on a target layer of a disk 850, and detects reflection from the target layer to obtain a signal S₁. The RF amplifier 804 then amplifies the signal S₁ to obtain a signal S₂. The DPD tracking error generator 812 then uses a differential phase detection method to synthesize a first tracking error signal TE_(DPD) according to the signal S₂. The DPP tracking error generator 814 then uses a differential push-pull method to synthesize a second tracking error signal TE_(DPP) according to the signal S₂.

When a layer jump operation starts, a layer jump signal is enabled, and the switch module 818 then generates a signal K to switch to a tracking error generation method. If the initial tracking error generation method is a DPP method, the tracking error generation method is then switched to a DPD method. If the initial tracking error generation method is a DPD method, the tracking error generation method is then switched to a DPP method. The multiplexer 816 then selects a tracking error signal TE from the first tracking error signal TE_(DPD) and the second tracking error signal TE_(DPP) according to the signal K generated by the switch module 818. A plurality of compensator parameters of the TE compensator 806 are also determined according to the tracking error generation method. The TE compensator 806 then generates a tracking control output signal TRO according to the tracking error signal TE and the compensator parameters for moving the laserbeam along a track of the target layer. In one embodiment, the tracking control output signal TRO is sent to the actuator driver 808, and the actuator driver 808 then moves the pickup head 802 along the track of the target layer according to the tracking control output signal TRO.

Referring to FIG. 9, a block diagram of another embodiment of an optical disk drive 900 performing a layer jump operation according to the invention is shown. The optical disk drive 900 comprises all component modules of the optical disk drive 800 shown in FIG. 8. In one embodiment, the optical disk drive 900 comprises a pickup head 902, a radio frequency (RF) amplifier 904, a tracking error compensator 906, an actuator driver 908, a DPD tracking error generator 912, a DPP tracking error generator 914, a multiplexer 916, a switch module 918, a focusing error generator 922, and a focusing error compensator 924. The circuits 902˜918 have the same functions as the corresponding circuits 802˜818. When a layer jump signal is enabled, the switch module 918 switches the tracking error generation method by a signal K, and determines a plurality of compensator parameters according to the switched tracking error generation method. After the multiplexer 916 selects the tracking error signal TE according to the signal K, the tracking error compensator 906 then adjusts a gain and a phase of the tracking error signal TE according to the compensator parameters, and generates a tracking control output signal TRO according to the adjusted tracking error signal. In addition, the optical disk drive 900 further comprises a focusing error generation module 922 for generating a focusing error signal FE according to the signal S₂, and a focusing error compensator 924 for generating a focus control output signal FRO for focusing a laserbeam on the target layer before or after the switch module 918 switches the tracking error generation method K.

While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. 

1. A method for performing a layer jump of a disk, comprising: determining a tracking error generation method according to a layer type of a target layer when the layer jump is performed; generating a tracking error signal according to the tracking error generation method.
 2. The method as claimed in claim 1, further comprising moving a laserbeam along a track of the target layer according to the tracking error signal.
 3. The method as claimed in claim 1, wherein determining of the tracking error generation method comprises: when the target layer is a BD-ROM layer, determining the tracking error generation method to be a differential phase detection (DPD) method; and when the target layer is a BD-RE layer or a BD-R layer, determining the tracking error generation method to be a differential push-pull (DPP) method.
 4. The method as claimed in claim 1, wherein the method further comprises: focusing a laserbeam on the target layer of the disk before the tracking error generation method is determined.
 5. The method as claimed in claim 1, wherein the method further comprises: focusing a laserbeam on the target layer of the disk after the tracking error generation method is determined.
 6. The method as claimed in claim 1, wherein the method further comprises: focusing a laserbeam on the target layer of the disk when the tracking error generation method is determined.
 7. The method as claimed in claim 1, wherein the method further comprises: determines a plurality of compensator parameters according to the tracking error generation method.
 8. The method as claimed in claim 1, wherein the step of moving the laserbeam along the track further comprises: adjusting a gain and a phase of the tracking error signal according to the tracking error generation method; generating a tracking control output signal according to the adjusted tracking error signal; and controlling a pickup head emitting the laser beam according to the tracking control output signal.
 9. The method as claimed in claim 1, wherein the disk is a BD Intra-Hybrid disk.
 10. An optical disk drive, performing a layer jump, comprising: a first tracking error generator, generating a first tracking error signal according to a differential phase detection (DPD) method; a second tracking error generator, generating a second tracking error signal according to a differential push-pull (DPP) method; a decision module, determining a tracking error generation method according to a layer type of a target layer of a disk when the layer jump is performed; and a multiplexer, selecting a tracking error signal from the first tracking error signal and the second tracking error signal according to the tracking error generation method.
 11. The optical disk drive as claimed in claim 10, wherein the optical disk drive comprises: a tracking error compensator, generating a tracking control output signal according to the tracking error signal for controlling a laserbeam along a track of the target layer.
 12. The optical disk drive as claimed in claim 10, wherein the decision module determines the tracking error generation method to be a differential phase detection (DPD) method when the target layer is a BD-ROM layer, and determines the tracking error generation method to be a differential push-pull (DPP) method when the target layer is a BD-RE layer or a BD-R layer.
 13. The optical disk drive as claimed in claim 10, wherein the optical disk drive further comprises: a focusing error generator, generating a focusing error signal; and a focusing error compensator, focusing the laserbeam on the target layer of the disk according to the focusing error signal before the tracking error generation method is determined.
 14. The optical disk drive as claimed in claim 10, wherein the optical disk drive further comprises: a focusing error generator, generating a focusing error signal; and a focusing error compensator, focusing the laserbeam on the target layer of the disk according to the focusing error signal after the tracking error generation method is determined.
 15. The optical disk drive as claimed in claim 11, wherein the decision module determines a plurality of compensator parameters according to the tracking error generation method, and the tracking error compensator generates the tracking control output signal according to the adjusted tracking error signal.
 16. The optical disk drive as claimed in claim 10, wherein the disk is a BD Intra-Hybrid disk.
 17. A method for performing a layer jump of a disk, wherein the disk comprises only a BDROM layer and a BD-RE/R layer, the method comprising: switching a tracking error generation method between a differential phase detection (DPD) method and a differential push-pull (DPP) method when the layer jump is performed; and generating a tracking error signal according to the tracking error generation method.
 18. The method as claimed in claim 17, wherein the method further comprises: focusing a laserbeam on the target layer of the disk before the tracking error generation method is switched.
 19. The method as claimed in claim 17, wherein the method further comprises: focusing a laserbeam on the target layer of the disk after the tracking error generation method is switched.
 20. The method as claimed in claim 17, wherein the method further comprises: focusing a laserbeam on the target layer of the disk when the tracking error generation method is determined.
 21. The method as claimed in claim 17, wherein the tracking error generation method is switched to the differential phase detection (DPD) method when the target layer is the BD-ROM layer, and the tracking error generation method is switched to be the differential push-pull (DPP) method when the target layer is the BD-RE/R layer.
 22. The method as claimed in claim 17, wherein the step of moving the laserbeam along the track further comprises: generating a tracking control output signal according to the adjusted tracking error signal; and controlling a pickup head emitting the laser beam according to the tracking control output signal.
 23. An optical disk drive, performing a layer jump on a disk, wherein the disk comprises only a BDROM layer and a BD-RE/R layer, and the optical disk drive comprises: a first tracking error generator, generating a first tracking error signal according to a differential phase detection (DPD) method; a second tracking error generator, generating a second tracking error signal according to a differential push-pull (DPP) method; a switch module, switching a tracking error generation method between the DPD method and the DPP method when the layer jump is performed; and a multiplexer, selecting a tracking error signal from the first tracking error signal and the second tracking error signal according to the tracking error generation method.
 24. The optical disk drive as claimed in claim 23, wherein the switch module switches the tracking error generation method to the differential phase detection (DPD) method when the target layer is the BD-ROM layer, and switches the tracking error generation method to the differential push-pull (DPP) method when the target layer is the BD-RE/R layer.
 25. The optical disk drive as claimed in claim 23, wherein the optical disk drive further comprises: a focusing error generator, generating a focusing error signal; and a focusing error compensator, focusing the laserbeam on the target layer of the disk according to the focusing error signal before the tracking error generation method is switched.
 26. The optical disk drive as claimed in claim 23, wherein the optical disk drive further comprises: a focusing error generator, generating a focusing error signal; and a focusing error compensator, focusing the laserbeam on the target layer of the disk according to the focusing error signal after the tracking error generation method is switched.
 27. The optical disk drive as claimed in claim 23, wherein the optical disk drive comprises: a tracking error compensator, generating a tracking control output signal according to the tracking error signal for controlling the laserbeam to move along a track of the target layer.
 28. The optical disk drive as claimed in claim 27, wherein the switch module determines a plurality of compensator parameters according to the switched tracking error generation method, and generates the tracking control output signal according to the adjusted tracking error signal. 